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著者人数: 59名（所属. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS): 權, 靜美), Accepted: 2018-06-08, 資料番号: SA1180097000

We obtained a deep wide-field (32' ? 24') narrowband (?c = 4977?,?? = 77?) image of a field including the protocluster at z = 3.1 in the SSA22a field studied by Steidel et al. using the Subaru Telescope. The field we observed is about 10 times as large as that studied by Steidel et al. We detected 283 highly confident strong Ly? emitter candidates at z ~ 3.1 down to 25.8 AB mag with the observed equivalent width larger than 154 ?. These strong Ly? emitter candidates show a highly nonuniform distribution with the beltlike region of high surface density, which is found to extend over ~60 Mpc in comoving scale. The average number density of the strong Ly? emitter candidates in this high-density region is 3 times as high as that of a blank field. The probability of finding such a large-scale high-density peak is as small as 0.1% in the context of the CDM structure formation scenario, if we assume a linear bias parameter b ~ 4. In addition to these strong Ly? emitters, we also detected 49 Ly? absorbers, which show significant deficit in the narrowband image. We further detected 74 extended emitters, which have significant fluxes over the areas of 18 arcsec2 or more. Interestingly, both these absorbers and extended emitters show sky distributions very similar to that of the strong Ly? emitters. This supports the reality of the large-scale structure at z = 3.1 and suggests that galaxy formation preferentially occurs in the high-density region of strong Ly? emitters.

We present the results of a survey for emission-line objects, based on optical intermediate-band (λc = 5736 A and Δλ = 280 A) and broadband (B, V, R, and i') observations of the Subaru/XMM-Newton Deep Field with the 8.2 m Subaru telescope and the Subaru Prime Focus Camera (Suprime-Cam). All the data were obtained during the guaranteed time observations of the Suprime-Cam instrument. The intermediate-band image covered a sky area of 1062 × 1240 ≈ 132 arcmin2 in the Subaru/XMM-Newton Deep Field (Ouchi et al.). Using this image, we found 23 emission-line sources whose observed emission-line equivalent widths are greater than 250 A. Their optical multicolor properties indicate that six emission-line sources are Lyα emitters at z ≈ 3.7 (Δz ≈ 0.22). They are either intense starburst galaxies or active galactic nuclei–like quasars at z ≈ 3.7. Two more emission-line sources may also be Lyα emitters at z ≈ 3.7, although their multicolor properties are marginal. Among the remaining 15 emission-line objects, eight objects appear to be strong emission-line galaxies at lower redshift; e.g., [O II] λ3727 emitters at z ≈ 0.54, Hβ at z ≈ 0.18, or [O III] λ5007 emitters at z ≈ 0.15. The remaining seven objects are unclassified because they are too faint to be detected in broadband images. We discuss the observational properties of these strong emission-line sources. In particular, our data allow us to estimate the star formation density at z ≈ 3.7 for the first time.

We present the results of the extensive narrow-band survey of Ly\alpha\ emission-line objects at z=3.1 in the 1.38 deg^2 area surrounding the high density region of star-forming galaxies at z=3.09 in the SSA22 field, as well as in the 1.04 deg^2 area of the three separated general blank fields. In total of 2161 Ly\alpha\ emitters, 1394 in the SSA22 fields and 767 in the general fields, respectively, are detected to the narrow-band AB magnitude limit of 25.73, which corresponds to the line flux of 1.8 x 10^{-17} erg s^{-1} cm^{-2} or luminosity of 1.5 x 10^{42} erg s^{-1} at z=3.1, above the observed equivalent width threshold, 190A. The average surface number density of the emitters at z=3.1 in the whole general fields above the thresholds is 0.20+-0.01 arcmin^{-2}. The SSA22 high-density region at z=3.09 whose peak local density is 6 times the average is found to be the most prominent outstanding structure in the whole surveyed area and is firmly identified as a robust `protocluster' with the enough large sample. We also compared the overdensity of the 100 arcmin^2 and 700 arcmin^2 areas which contain the protocluster with the expected fluctuation of the dark matter as well as those of the model galaxies in cosmological simulations. We found that the peak height values of the overdensity correspond to be 8-10 times and 3-4 times of the expected standard deviations of the counts of Ly\alpha emitters at z=3.1 in the corresponding volume, respectively. We conclude that the structure at z=3.09 in the SSA22 field is a very significant and rare density peak up to the scale of 60 Mpc.